Unlike the existing needles, micronneedles pass through skin without pain and do not leave an external injury. In order to implant a microneedle into skin without pain, a diameter of an upper portion of the microneedle is important for the minimum sharpness. Also, the microneedles needs to pass through a stratum corneum of 10 μm to 20 μm serving as the biggest obstacle in skin, and thus are required to have sufficient physical hardness. However, since the thicknesses and elasticity of skins, efficiency of transdermal drug delivery, the viscosities of drugs, and the amount of administered drugs differ according to species, races, individuals, and skin regions, a method for manufacturing a microneedle having a variable appearance is required.
A hollow silicon microneedle having a bevel angle was developed by Nanopass company in a secondary etching method which is an advanced etching method (WO 0217985; WO 2005049107; Gardeniers, Han J. G. E, et al., Silicon Micromachined Hollow Microneedles for Transdermal Liquid Transport, Journal of microelectro-chemical systems, 12(6): 855-862 (2003)). Griss and Stemme of Stanford University in the USA have proposed a side-opened hollow silicon microneedle and a cross-type hollow silicon microneedle (P. Griss and G. Stemme, Side-Opened Out-of-Plane Microneedles for Microfluidic Transdermal Liquid Transfer, Journal of microelectro-chemical systems, 12(3): 296301 (2003); U.S. Patent Publication No. 2004-0267205).
Prausnitz of Georgia University in the USA proposed a method that forms a mold with a laser and manufactures a hollow microneedle by using deposition and electro-plating (Prausnitz, M. R. et al., Hollow Metal Microneedles for Insulin Delivery to Diabetic Rats IEEE, Transaction on biomedical engineering, 52(5): 909-915 (2005)). However, the hollow microneedle manufactured by the method has problems in diameter and length similarly to the above-described methods. Also, Prausnitz of Georgia University in the USA proposed a new-type hollow glass microneedle that has a bevel angle and a length of about 900 μm formed by lengthening a glass micropipette at a high temperature (“Microinfusion Using Hollow Microneeldes”, Pharmaceutical Research, Vol. 23, No. 1, January 2006 and “Mechanism of fluid infusion during microneedle insertion and retraction”, Journal of Controlled Release, 2006, 357361). As described above, various hollow microneedles have been developed. However, since the hollow microneedles are manufactured as standardized products to have uniform appearances in length, diameter, aspect ratio, sharpness, and bevel angle, it is difficult for the products of currently standardized hollow microneedles to deliver drugs through various regions of a human body and perform efficient conversion according to drugs having various viscosities, and the medical application of the hollow microneedles are limited compared to the existing hypodermic needle. Therefore, it is continuously required manufacturing technology in which the strength, sharpness, bevel angle, and bending of a hollow microneedle necessary for passing through skin may be adjusted depending on regions of skin, the length of the hollow microneedle may be adjusted according to a degree by which the hollow microneedle passes through skin, and, by adjusting the diameter of the hollow microneedle according to the change in the viscosity and administration amount of treated drug, the external appearance of the hollow microneedle may be flexibly adjusted according to the application method of drug delivery and body material sampling including blood collection.
In the specification, a plurality of papers and patent documents are referenced, and citations thereof are indicated. The overall disclosure of each of the cited paper and patent document is inserted as a reference into the specification, and thus, the level of the technical field of the present invention and the configuration and function of the present invention are clearly described.